Anatomy lesson anyone...?

Adult mice have more calcium in their tiny bones than a unweaned rat. The rats still suckling off their mom are still mostly rubber(cartilage), as are just weaned rats, still some cartilage in the place of bone. It's just based on the age of the rodent as to how much the bone-cartilage ratio varies. We've learned about this in anatomy about puppies and kittens. When they are born, they could probably bounce they are so rubbery.

So Kontron, if an adult mouse still makes a lump, then I would stay on those until a weaned rat would fit in the snakes tummy. Because IMO, rats that aren't weaned yet just don't provide enough calcium for growing babies and juveniles.